1. Field of the Invention
The present invention relates to an automatic developing apparatus in which a film transport unit provided with film transport rollers is sunk in a treatment tank containing treatment liquid used for developing film or a similar photosensitive material. In particular, the present invention relates to an automatic developing apparatus where torque is transmitted from outside of the treatment tank to the film transport rollers through the liquid surface in the treatment tank.
2. Discussion of the Related Art
Automatic developing apparatus generally include a plurality of treatment tanks 52 containing treatment liquids 51 which are liquid agents such as developer, bleaching liquid and fixer, for example, as shown in FIG. 4. Transport units (hereinafter, "rack") 53 containing a plurality of transport rollers for transporting a photosensitive material such as film are sunk in the respective treatment tanks 52. In this way, the film can be developed by being immersed in the respective treatment liquids 51 while being transported through the respective treatment tanks 52. The film, developed by passage through the respective treatment tanks 52, is then transported to a drying assembly (not shown) to be dried and discharged from the apparatus.
The aforementioned plurality of transport rollers of the rack 53 include a pair of feed rollers 54a, 54b, large-diameter rollers 55a, 55b, 55c, first small-diameter rollers 56a, 56b, 56c, second small-diameter rollers 57a, 57d, 57c, and reverse rollers (not shown). These rollers are provided so that the axis of rotations thereof all are along the widthwise direction of the film. The reverse rollers are provided at the bottom end of the rack 53 without being held in contact with any other roller, and the transport direction of the film being transported is reversed by being moved along the circumferential surface of the reverse rollers.
The feed rollers 54a, 54b introduce the film into the treatment tank 52 and are positioned near a film inlet so as to face each other.
The large-diameter roller 55a is provided in an inner upper portion of the rack 53 such that a portion of its circumferential surface crosses the liquid surface L of the treatment liquid 51 in the treatment tank 52. The large-diameter rollers 55b, 55c, are provided in this order in a downward direction from the large-diameter roller 55a so that the interval between successive rollers (including the interval between the large-diameter rollers 55a and 55b) are substantially equal, and are completely immersed in the treatment liquid 51.
The first small-diameter rollers 56a, 56b, 56c, are positioned to face the large-diameter rollers 55a, 55b, 55c, so that the film introduced by the pair of feed rollers 54a, 54b can be transported by the rotation of the respective pairs of the large-diameter and small-diameter rollers while being tightly held.
The second small-diameter rollers 57a, 57b, 57c, are positioned to face the large-diameter rollers 55a, 55b 55c, at the side opposite from the first small-diameter rollers 56a, 56b, 56c, so that the film having its transport direction reversed by the reverse rollers can be transported by the rotation of the respective pairs of the large-diameter and small-diameter rollers while being tightly held.
Torque imparted to these transport rollers is transmitted from a drive source (not shown) outside the treatment tank 52 via gears and spur gears provided in the treatment tank 52. Hereinafter, the principle of rotating the respective transport rollers is described with reference to FIGS. 4 and 5.
The large-diameter rollers 55a, 55b, 55c, the first smalldiameter rollers 56a, 56b, 56c, and the second small-diameter rollers 57a, 57b, 57c, shown in FIG. 4 are connected with first spur gears 65a, 65b, 65c, second spur gears 66a, 66b, 66c, and the third spur gears 67a, 67b, 67c, while sharing the same rotatable shafts. The first spur gears 65a, 65b, 65c, are in mesh with the second spur gears 66a, 66b, 66c, and also with the third spur gears 67a, 67b, 67c, respectively.
The first spur gear 65a integrally positioned with the large-diameter roller 55a is positioned such that a portion of the teeth on its circumferential surface crosses the liquid surface L of the treatment liquid 51 in the treatment tank 52 when the rack 53 is set in the treatment tank 52. Further, the reverse rollers are connected to the first spur gear located in the bottommost position in the rack 53 while sharing the same rotatable shaft.
Fourth spur gears 68a, 68b, 68c, are placed between the first spur gears 65a and 65b and between the first spur gears 65b and 65c, such that each is in mesh with the corresponding pair of the first spur gears. The first spur gear 65a located in the uppermost position in the rack 53 is in mesh with a fifth spur gear 70 provided coaxially with a gear 69, to which torque is transmitted from the drive source at the side opposite from the engaging portion with the fourth spur gear 68a.
It is noted that spur gears provided coaxially with feed rollers 54a, 54b (see FIG. 4) are not illustrated. However, the torque from the drive source is transmitted to the feed rollers 54a, 54b at least via, e.g. the fifth spur gear 70 so that the feed rollers 54a, 54b are rotated to introduce the film between the large-diameter roller 55a and the first small-diameter roller 56a.
In the above construction, if torque from the drive source is used to simultaneously rotate the gear 69 and the fifth spur gear 70 in, e.g. a direction E of FIG. 5, the first spur gear 65a in mesh with the fifth spur gear 70 is rotated in a direction F which is opposite from the direction E. The second spur gear 66a, the third spur gear 67a and the fourth spur gear 68a which are in mesh with the fifth spur gear 65a are rotated in the direction E. The first spur gear 65b in mesh with the fourth spur gear 68a is rotated in the direction F by the rotation of the fourth spur gear 68a in the direction E, with the result that the second spur gear 66b, the third spur gear 67b and the fourth spur gear 68a which are in mesh with the first spur gear 65b are rotated in the direction E.
Thereafter, the large-diameter rollers 55a, 55b, 55c, provided coaxially with the first spur gears 65a, 65b, 65c, are all rotated in the direction F by the rotation of all the first spur gears 65a, 65b, 65c, in the direction F. On the other hand, the first small-diameter rollers 56a, 56b, 56c, and the second small-diameter rollers 57a, 57b, 57c, are all rotated in the direction E by the rotation of all the second spur gears 66a, 66b, 66c and all the third spur gears 67a, 67b, 67c, in the direction E.
Accordingly, as shown in FIG. 4, the film is passed through the film inlet (not shown) and passed between the feed rollers 54a, 54b. Then the film is transported to the lower side while being successively passed between the large-diameter roller 55a and the first small-diameter roller 56a and between the large-diameter roller 55b and the first small-diameter roller 56b, by the rotation of the large-diameter rollers 55 and the first small-diameter rollers 56. After the transport direction of the film is reversed by the reverse rollers, the film is transported upward from the lower side while passing between the corresponding pairs of the large-diameter rollers 55 and the second small-diameter rollers 57 by the rotation of the large-diameter rollers 55 and the second small-diameter rollers 57. Thereafter, the film is transported to the next treatment tank 52 while passing between the large-diameter roller 55a and second small-diameter roller 57a. In other words, the film passes along a film transport path indicated by P in FIG. 4.
FIG. 6 is a cross sectional view along line A--A of FIG. 4. As shown in FIG. 6, slit-shaped outlets 58 are formed in positions corresponding to the film transport path inside the rack 53, and the treatment liquid 51 is placed into the treatment tank 52 through the outlets 58.
In a conventional developing apparatus, a part of the irregularity on the circumferential surface of the first spur gear 65a having an axis of rotation in parallel with the liquid surface L of the treatment liquid 51 crosses the liquid surface L of the treatment liquid 51 in the treatment tank 52. Accordingly, while the first spur gear 65a is rotated, the treatment liquid 51 is scooped up by the teeth (projections) of the first spur gear 65a and, therefore, it is either directly deposited on the teeth or it falls after being scooped up, thereby mixing with the treatment liquid 51 in the treatment tank 52.
Here, in the case of deposition on the teeth, the scooped treatment liquid 51 also passes onto the second spur gear 66a, the third spur gear 67a and the fifth spur gear 70 in mesh with the first spur gear 65a and is solidified on the circumferential surfaces of these spur gears. This results in added weight acting on the torque transmission from the drive source and unsatisfactory torque transmission, thereby hindering film transport.
On the other hand, in the case where the liquid falls back into the tank, since the treatment liquid 51 is frequently brought into contact with air by being scooped up, oxidation of the treatment liquid 51 is promoted. This oxidation reduces the usefulness of the treatment liquid 51. In addition, evaporation of the liquid increases, thereby decreasing the amount of treatment liquid 51 which is predetermined in accordance with required specifications. As a result, satisfactory development cannot always be achieved.